The focus of this research is the analysis of the cellular expression of viral gene products in relation to cell function. Two main studies are planned: one concerned with the expression of endogeneous oncornavirus proteins at the cell surface and another, with the analysis of a relationship between endogeneous oncornaviruses and resistance to tumorigenesis. A principle objective is a definition of the organization and relatedness of viral and cellular proteins at the cell surface. Monoclonal antibodies synthesized by myeloma-spleen cell hybrids and reactive with the cell surface molecules of cultured mouse fibroblast cells are being prepared and analyzed. Those antibodies that precipitate cell membrane proteins will be used as probes to study the structure the organization of these proteins in relation to previously purified and characterized proteins of cell endogeneous oncornaviruses. Previous work has shown a possible correlation between tumorigenesis and the expression of endogenous oncornaviruses. Studies of the mechanism of this effect, as in the induction or control of tumor growth, will be initiated. This will include the analysis of the types of endogeneous viruses associated with resistance to tumorigenesis, the genetics and viral transmission of the effect, and the site of action.